JPS60218123A - Laser beam positioning device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a laser beam positioning device used to irradiate a measurement target with a laser beam when measuring physical quantities such as velocity and displacement using a laser beam. It is related to.

[Prior Art] FIG. 1 is a block diagram of a conventional laser beam positioning device. In the figure, (1) is a laser light source, (2) is an optical deflector, (3) is a control circuit for optical deflector (2), and (4) is a control circuit for optical deflector (2).
) is a deflected laser beam, and (5) is a photodetector.

Next, the operation will be explained. A laser beam (4) emitted from a laser light source (1) is two-dimensionally scanned within a plane on which a photodetector (5) is installed by an optical deflector (2). When the laser beam (4) is detected by the photodetector (5) during laser beam scanning, the photodetector (5) sends a signal to the control circuit (3) of the optical deflector (2).

This positions the laser beam (4) in the direction of the photodetector (5).

The conventional laser beam positioning device performs two-dimensional scanning of the laser beam (4) as described above.
), the disadvantage is that it takes a long time for positioning.

[Summary of the invention] This invention was made to eliminate the drawbacks of the conventional ones as described above, and instead of scanning a laser beam two-dimensionally using an optical deflector, it uses an optically rough surface object The object of the present invention is to provide a laser beam positioning device that can perform positioning in a shorter time than two-dimensional scanning by diffusing a laser beam and generating an interference pattern with a two-dimensional intensity distribution.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows an example of a laser beam positioning device according to the present invention, and the same parts as in FIG.

In the figure, (21) is an optically rough object such as ground glass, and the laser beam (4) from the laser light source (1)
The beam is phase-modulated and diffused irradiation is performed. (22) is the rotation mechanism of the rough surface object (21), and the laser beam (4
) The rough surface object (21) is rotated around the irradiated point. (23) is a photodetector (5)
A signal processing circuit that measures the time fluctuation of the output from (24
) is a drive mechanism for a block consisting of the laser light source (1) and the rough surface object (21), and receives the IN force from the signal processing circuit (23) to drive the light source ( 1) changes the direction.

The signal processing circuit (23) may be, for example, a DC component removal circuit (51) that removes a DC component from the output of the photodetector (5) as shown in FIG.
It is composed of a multiplication circuit (52) and a V digestion circuit (53).

Next, the operation of the above configuration will be explained.

Laser beam (4) emitted by laser light source (1)
is phase-modulated and diffusely irradiated by the rough surface object (21). For this reason, on the observation surface where the photodetector (5) is placed, an interference pattern with a granular intensity distribution called a speckle pattern is created, and the roughly rough object (21) is exposed to the laser beam (4). The speckle pattern also performs rotational movement by being rotated by the rotation mechanism (22) around the point where it is irradiated. Photodetector (
When the light intensity detected in step 5) deviates from the center of the laser beam (4), the time fluctuation of the light intensity is large as shown in Figure 3, and as it approaches the center, the fluctuation becomes smaller as shown in Figure 4. Become. Therefore, the temporal fluctuation of the light intensity detected by the photodetector (5) is measured using the signal processing circuit (23). In other words, the light intensity signal (Fig. 6 (A)) which is the output from the photodetector (5) described in 2. After the DC component is removed, the signal is input to the squaring circuit (52). The output from the squaring circuit (52) (Fig. 6 (C)) is smoothed by the smoothing circuit (53) as shown in Fig. 6 (D), in other words, the output from the square circuit (52) is smoothed as shown in Fig. 6 (D). voltage will be obtained. When this is applied as a measurement signal to the drive mechanism (8), the drive mechanism (20) positions the laser beam (4) in the direction in which the above-mentioned time fluctuation becomes smaller.

Here, the laser beam (4) is diffused using the rough surface object (21) described in 1. to generate an interference pattern with a two-dimensional intensity distribution, and the direction in which the temporal fluctuation of the detection output of this is reduced is Since the emission direction of the laser beam (4) is controlled, the laser beam (4) can be positioned in a shorter time than the scanning time of two-dimensional scanning.

[Effects of the Invention] As described in Part 2, according to the present invention, an optically rough surface object is irradiated with a laser beam to generate an interference pattern with a two-dimensional intensity distribution, and the deflection is determined from the output of the detected interference pattern. Since it is configured to control, there is no need to scan the laser beam, and positioning can be performed in a short time.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing a conventional laser beam positioning device, FIG. 2 is a block diagram showing an example of a laser beam positioning device according to the present invention, and FIGS. The figures are diagrams showing the relationship between light intensity and time in states where the fluctuation of light intensity over time is large and small, respectively. Fig. 5 is a block diagram showing the specific configuration of the signal processing circuit, and Figs. 6 (A) to (
D) is a signal waveform diagram of each part of the signal processing circuit. (1)... Laser beam, (4)... Laser beam,
(5)...Photodetector, (21)...Optical rough surface object, (22)...Rotation mechanism, (23)...Signal processing circuit, (24)...Drive mechanism. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Figure 5 Figure 6 Procedural amendment (voluntary) 1. Indication of the case: Japanese Patent Application No. 59-075231 2. Name of the invention: Laser beam positioning device 3. Representative of the person making the amendment: Katayuni Kata Part 4, Agent 5, “Brief explanation of drawings” column of the specification subject to amendment. 6. Contents of amendment (1) The description is amended as follows. (2)

Claims (1)

[Claims] (1) A laser light source, an optically rough object that diffuses the laser beam from the laser light source to generate an interference pattern with a two-dimensional intensity distribution, and rotates this rough object around the irradiation point of the laser beam. a rotation mechanism for rotating the laser beam, a photodetector for the laser beam, a signal processing circuit that measures the variation over time of the light intensity signal from the photodetector and outputs a signal proportional to the variation, and a signal from the signal processing circuit. and a drive mechanism that deflects the laser beam in a direction in which the above-mentioned fluctuation is reduced.